Method setdefault

Lib/weakref.py:224–233

(self, key, default=None)

            return o

    def setdefault(self, key, default=None):
        try:
            o = self.data[key]()
        except KeyError:
            o = None
        if o is None:
            self.data[key] = KeyedRef(default, self._remove, key)
            return default
        else:
            return o

    def update(self, other=None, /, **kwargs):
        d = self.data